QWSLock Class Reference

#include <qwslock_p.h>

Public Types
enum	LockType { BackingStore, Communication, RegionEvent }

Public Functions
bool	hasLock (LockType type)
int	id () const
bool	lock (LockType type, int timeout=-1)
	QWSLock (int lockId=-1)
void	unlock (LockType type)
bool	wait (LockType type, int timeout=-1)
	~QWSLock ()

Private Functions
bool	down (unsigned short semNum, int timeout)
int	getValue (unsigned short semNum) const
bool	up (unsigned short semNum)

Properties
int	lockCount [2]
int	semId

Detailed Description

Definition at line 66 of file qwslock_p.h.

Enumerations

LockType

enum QWSLock::LockType

Enumerator
BackingStore
Communication
RegionEvent

Definition at line 69 of file qwslock_p.h.

{ BackingStore, Communication, RegionEvent };

Constructors and Destructors

QWSLock()

QWSLock::QWSLock

(

int

lockId = -1

)

Definition at line 78 of file qwslock.cpp.

                       : semId(id)
{
    static unsigned short initialValues[3] = { 1, 1, 0 };

#ifndef QT_NO_QWS_SIGNALHANDLER
    QWSSignalHandler::instance()->addWSLock(this);
#endif

#ifndef QT_POSIX_IPC
    if (semId == -1) {
        semId = semget(IPC_PRIVATE, 3, IPC_CREAT | 0666);
        if (semId == -1) {
            perror("QWSLock::QWSLock");
            qFatal("Unable to create semaphore");
        }

        qt_semun semval;
        semval.array = initialValues;
        if (semctl(semId, 0, SETALL, semval) == -1) {
            perror("QWSLock::QWSLock");
            qFatal("Unable to initialize semaphores");
        }
    }
#else
    sems[0] = sems[1] = sems[2] = SEM_FAILED;
    owned = false;

    if (semId == -1) {
        // ### generate really unique IDs
        semId = (getpid() << 16) + (localUniqueId.fetchAndAddRelaxed(1) % ushort(-1));
        owned = true;
    }

    QByteArray pfx = "/qwslock_" + QByteArray::number(semId, 16) + '_';
    QByteArray keys[3] = { pfx + "BackingStore", pfx + "Communication", pfx + "RegionEvent" };
    for (int i = 0; i < 3; ++i) {
        if (owned)
            sem_unlink(keys[i].constData());
        do {
            sems[i] = sem_open(keys[i].constData(), (owned ? O_CREAT : 0), 0666, initialValues[i]);
        } while (sems[i] == SEM_FAILED && errno == EINTR);
        if (sems[i] == SEM_FAILED) {
            perror("QWSLock::QWSLock");
            qFatal("Unable to %s semaphore", (owned ? "create" : "open"));
        }
    }
#endif

    lockCount[0] = lockCount[1] = 0;
}

~QWSLock()

QWSLock::~QWSLock

(

)

Definition at line 129 of file qwslock.cpp.

Referenced by QWSSignalHandler::clear().

{
#ifndef QT_NO_QWS_SIGNALHANDLER
    QWSSignalHandler::instance()->removeWSLock(this);
#endif

    if (semId != -1) {
#ifndef QT_POSIX_IPC
        qt_semun semval;
        semval.val = 0;
        semctl(semId, 0, IPC_RMID, semval);
        semId = -1;
#else
        // emulate the SEM_UNDO behavior for the BackingStore lock
        while (hasLock(BackingStore))
            unlock(BackingStore);

        QByteArray pfx = "/qwslock_" + QByteArray::number(semId, 16) + '_';
        QByteArray keys[3] = { pfx + "BackingStore", pfx + "Communication", pfx + "RegionEvent" };
        for (int i = 0; i < 3; ++i) {
            if (sems[i] != SEM_FAILED) {
                sem_close(sems[i]);
                sems[i] = SEM_FAILED;
            }
            if (owned)
                sem_unlink(keys[i].constData());
        }
#endif
    }
}

Functions

down()

bool QWSLock::down ( unsigned short  semNum, int  timeout  )

private

Definition at line 185 of file qwslock.cpp.

Referenced by id(), lock(), unlock(), and wait().

{
    int ret;

#ifndef QT_POSIX_IPC
    sembuf sops = { semNum, -1, 0 };
    // As the BackingStore lock is a mutex, and only one process may own
    // the lock, it's safe to use SEM_UNDO. On the other hand, the
    // Communication lock is locked by the client but unlocked by the
    // server and therefore can't use SEM_UNDO.
    if (semNum == BackingStore)
        sops.sem_flg |= SEM_UNDO;

    EINTR_LOOP(ret, semop(semId, &sops, 1));
#else
    EINTR_LOOP(ret, sem_wait(sems[semNum]));
#endif
    if (ret == -1) {
        qDebug("QWSLock::down(): %s", strerror(errno));
        return false;
    }

    return true;
}

getValue()

int QWSLock::getValue ( unsigned short  semNum ) const

private

Definition at line 210 of file qwslock.cpp.

Referenced by hasLock(), and id().

{
    int ret;
#ifndef QT_POSIX_IPC
    ret = semctl(semId, semNum, GETVAL, 0);
#else
    if (sem_getvalue(sems[semNum], &ret) == -1)
        ret = -1;
#endif
    if (ret == -1)
        qDebug("QWSLock::getValue(): %s", strerror(errno));
    return ret;
}

hasLock()

bool QWSLock::hasLock

(

LockType

type

)

Definition at line 242 of file qwslock.cpp.

Referenced by ~QWSLock().

{
    if (type == RegionEvent)
        return getValue(type) == 0;

    return lockCount[type] > 0;
}

id()

int QWSLock::id ( ) const

inline

Definition at line 78 of file qwslock_p.h.

Referenced by QWSSharedMemSurface::permanentState(), QWSDisplay::setIdentity(), and QWSMemorySurface::setLock().

{ return semId; }

lock()

bool QWSLock::lock	(	LockType	type,
		int	timeout = -1
	)

Definition at line 224 of file qwslock.cpp.

{
    if (type == RegionEvent)
        return up(type);

    if (lockCount[type] > 0) {
        ++lockCount[type];
        return true;
    }

    if (down(type, timeout)) {
        ++lockCount[type];
        return true;
    }

    return false;
}

unlock()

void QWSLock::unlock

(

LockType

type

)

Definition at line 250 of file qwslock.cpp.

Referenced by wait(), and ~QWSLock().

{
    if (type == RegionEvent) {
        down(type, -1);
        return;
    }

    if (lockCount[type] > 0) {
        --lockCount[type];
        if (lockCount[type] > 0)
            return;
    }

    up(type);
}

up()

bool QWSLock::up ( unsigned short  semNum )

private

Definition at line 160 of file qwslock.cpp.

Referenced by id(), lock(), and unlock().

{
    int ret;

#ifndef QT_POSIX_IPC
    sembuf sops = { semNum, 1, 0 };
    // As the BackingStore lock is a mutex, and only one process may own
    // the lock, it's safe to use SEM_UNDO. On the other hand, the
    // Communication lock is locked by the client but unlocked by the
    // server and therefore can't use SEM_UNDO.
    if (semNum == BackingStore)
        sops.sem_flg |= SEM_UNDO;

    EINTR_LOOP(ret, semop(semId, &sops, 1));
#else
    ret = sem_post(sems[semNum]);
#endif
    if (ret == -1) {
        qDebug("QWSLock::up(): %s", strerror(errno));
        return false;
    }

    return true;
}

wait()

bool QWSLock::wait	(	LockType	type,
		int	timeout = -1
	)

Definition at line 266 of file qwslock.cpp.

{
    bool ok = down(type, timeout);
    if (ok)
        unlock(type);
    return ok;
}

Properties

lockCount

int QWSLock::lockCount[2]

private

Definition at line 86 of file qwslock_p.h.

Referenced by hasLock(), lock(), QWSLock(), and unlock().

semId

int QWSLock::semId

private

Definition at line 85 of file qwslock_p.h.

Referenced by down(), getValue(), id(), QWSLock(), up(), and ~QWSLock().

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The documentation for this class was generated from the following files:

• /src/gui/embedded/qwslock_p.h
• /src/gui/embedded/qwslock.cpp